Mild hydrogenation process for lubricating oils



E. L. COLE Sept. l5, 1959 MILD HYDROGENATION PROCESS FOR LUBRICATING OILS Filed June 16, 1955 .im ,l S x Q b @f w n xv,

nited States Patent MILD HYDROGENATION PROCESS FR LUBRICATING OILS v Edward L. Cole, Glenham, N.Y., assignor to Texaco Inc., incorporation of Delaware Application .lune 16, 1955, Serial No. 515,957

3 Claims. (Cl. 20S-264) This invention relates to improvements in the manufacture of lubricating oils. More particularly, it relates to a mild hydrogenation process to produce lubricating oils of high viscosity index and unexpectedly good color, stability and resistance to oxidation. In the process of this invention, a lubricating stock is subjected to mild hydrogenation conditions such that saturation reactions are suppressed. and splitting reactions are favored to produce a lubricating oil of improved stability and resistance to oxidation.

yLubricating oils are conventionally refined by methods including the steps of distillation, solvent refining, acid treating, clay contacting and solvent dewaxing. When residual type lubricating oils are processed, an additional step of deasphalting is usually required. In the processing steps listed-above, distillation is employed as a means of yseparating the crude oil into fractions of suitable Viscosity. Solvent refining, with, for example, furfural, sulfur dioxide or phenol, is ordinarily used as a means of removing cyclic compounds and thereby improving viscosity index of the treated oil. Viscosity index is an important characteristic of a lubricating oil indicative of the resistance of the oil to change in viscosity with change in temperature. Acid treating is employed to improve the color, stability and vresistance to oxidation of lubricating oils. Clay contacting is used to further improve the color and to neutralize the oil after acid treating. Solvent dewaxing is used to lower the pour point of the oil, and deasphalting is employed to remove asphaltic bodies.

All of the characteristics noted above, that is, viscosity range, viscosity index, color, stability, resistance to oxidation, pour point and freedom from asphaltic bodies are important. The requirements of various lubricating applications diier greatly so that different oil characteristics maybe limiting when manufacturing lubricating oils for different applications. Therefore to obtain a satisfactory lubricating oil, a balance of various characteristics is necessary depending upon the requirements of the intended application.

Mild hydrogenation of lubricating oil stocksl -is` known inthe prior art'as a' means vofretining.. an'oilv for the lice' improvement of viscosity index. This method of retining lubricating oils has an advantage over solvent reiining in that the yields of treated oil are much higher for the mild hydrogenation process. The present process is an improvement over prior processes for refining lubricating oil by mild hydrogenation. I have found that under certain conditions, mild hydrogenation maybe employed to achieve a substantial improvement not only in viscosity index of a lubricating oil, but, concomitantly, characteristics of unexpectedly good color, stability, and resistance to oxidation may be obtained. By the process of this invention, I have been able to accomplish with a single step of mild hydrogenation the results ordinarily requiring the three steps of solvent refining, acid treating and clay contacting.

In my invention a lubricating oil stock is subjected to mild hydrogenation conditions such that saturation reactions are suppressed and splitting :reactions are favored to produce a lubricating oil of improved stability and resistance to oxidation. In the process of this invention, conditions of temperature, pressure and space velocity are selected so that only a minor portion of the aromatics present in the feed are saturated to form non-aromatic hydrocarbons. I have found in a preferred embodiment of this invention that I may produce a lubricating oil of greatly improved stability and resistance to oxidation when hydrogenating under mild Vsplitting conditions such that about one-third of the aromatics contained in the feed are saturated leaving the remaining two-thirds of the aromatics unconverted. i

The process of this invention may be carried out ernploying a wide range of operating conditions,` for example, temperatures of 650 to 800 F., pressures of 500 to 5000 p..s.i. and Vspace velocities from 0.1 to 5.0 may be used. In a preferred embodiment of this invention, however, operating conditions comprising temperatures of 700 to 750 F., a pressure of 1000 to 2000 p.s.i.g. and a space velocity of 0.5 to 2.0 Volumes of o-il per volume of catalyst are used. n Within the narrower limits of the preferred range of conditions listed above, the

l conditions are not independently variable. It is, thereto produce naphthenic hydrocarbons.

fore, necessary to select conditions from within the ranges specified to accomplish mild splitting .as evidenced by the formation of hydrocarbons lower boiling than the feed and yet to effect only a minor amount of saturation of the aromatic hydrocarbons present. The interdependence of these operating variables will be more clearly understood by reference to the discussion following Table I. K

Hydrogen is consumed in the saturation of aromatics In the splitting reaction, cracking occurs to produce lower boiling hydrocarbons. Hydrogen is consumed in the course of the splitting reaction to saturate the olefins which are formed as a result of cracking. I have found that less hydrogen is consumed-in mild splitting as practiced in the process of my invention as compared with saturation hydrogenation or saturation-splitting hydrogenation. I have found that a product of improved stability and resistance to oxidation may be produced by my process when conditions are selected such that the hydrogen consumption is less than 500 cubic feet per barrel of feed.

A preferred catalyst for the process of this invention is a nickel sulde-tungsten sulde catalyst having a cornposition represented by the empirical formula:

However, nickel sulfide-tungsten sulde catalysts of other compositions, other hydrogenation catalysts such as molybdenum sullide, cobalt molybdate, supported noble metals and metals of the 6th and 8th groups of the periodic table, and oxides, sull'ldes, or mixtures thereof, may be employed for the process of this invention.

An advantage of this process is that it greatly improves the stability and resistance to oxidation as well as the viscosity index of a lubricating oil stock.

Another advantage of this process is that it accomplishes in one processing step the product quality irnprovement obtained with the three steps of solvent relining, acid treating and clay contacting employed in conventional rening of lubricating oil stocks.

Another advantage of this invention is 'that it produces high yields of lubricating oils and avoids the yield losses inherent in solvent rening and acid treating.

A further advantage of this invention in comparison with other mild hydrogenation processes is that under the mild splitting conditions employed, less hydrogen is consumed `than when saturating conditions are employed.

Another advantage of this process is that it permits the efiicient utilization of by-product hydrogen from catalytic reforming to produce lubricating oils of high quality and value.

The accompanying drawing diagrammatically illustrates the process of this invention. Although the drawing illustrates one arrangement of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus or material described.

A lubricating oil stock from external storage, not shown, is charged through line 1 in admixture with hydrogen from line 2 to heater 3. Heater eluent is transferred through line 3a to reactor 4 which contains a hydrogenation catalyst. The reactor effluent is withdrawn through line S, cooled in condenser 6 and directed through line 7 to gas liquid separator 8. Hydrogen gas from separator 8 is recycled through line 9 by means of compressor 10 and line 2. Build-up of undesirable components in the hydrogen recycle stream may be prevented by withdrawing a portion of the stream as purge gas through line 11. To supply hydrogen consumed in the mild hydrogenation reaction, withdrawn from the system in the purge gas, and dissolved in the liquid product, make-up hydrogen, from a source not shown, is admitted to the system through line 12 and combined with the recycle gas in line 2r Liquid from gas-liquid separator 8 is withdrawn through line 13 and charged to fractionator 14. Fractionator 14 is a fractional distillation means employed to separate the liquid product into off-gas which is Withdrawn through line 15, naphtha Withdrawn through line 16, kerosine Withdrawn through line 17, diesel fuel withdrawn through line 18, heavy gas oil Withdrawn through line 19 and hydrorefined lubricating stock Withdrawn through line 20. The hydroreiined lubricating stock in line 20 is charged to dewaxing means 21 from which hydrorened lubricat-l ing oil is withdrawn through line 22 and slack wax is dis-t charged through line 23.

'The invention is further illustrated in the following examples. A Wax distillate obtained by vacuum distillation of a parain base crude oil is subjected to mild hydrogenation over a nickel sulfide-tungsten sulde catalyst having a composition represented by the empirical formula lNiS-OJSWSZ under conditions of saturation, splittingsaturation, and mild splitting with the results shown in Table I.

TABLE I Hydrorefning wax distillate over nickel sulfide-tungsten sulfide catalyst lramnln A. B C

Type of run (1) (i) (3) Pressure, p s i g 1, 500 1, 500 Temperature, 67 732 Space velocity, v 1.0 Hydrogen recycle rate, cu. ft./bbl 4, 400 Hydrogen consumed, eu. ft./bbl 548 1, 020 342 Hydrorenlng yields, percent of feed:

Gas, Weight percent 0.29 0.57 0.61 Total liquid, volume percent 102. 5 106.0 102. 9

Yields after fractionation and dewaxing,

percent of feed:

Naphtha, volume percent 0. 6 2. 5 1. 4 Kerosne, volume percent,..- 2. 4 8.5 4. 3 Diesel fuel, volume percent 1.0 2. 3 1. 3 Heavy gas oil, volume percent 0.5 0.6 0. 3 Total light oils, volume percent` 4. 5 13.9 7. 3

Hydrorened lubricating oil, volume percent 84. 3 72. 2 79. 9 Slack, wax, volume percent 13. 7 19. 9 15. 7

Total lubricating oil stock, volume percent 98. 0 92. 1 95. 6

1 Saturation. 2 Splitting saturation.

3 Mild splitting.

In mild hydrogenation there are a number of competing reactions which proceed at varying rates depending upon the operating conditions employed. Restricting consideration to the reactions of the hydrocarbon components of a lubricating oil, the two predominant mild hydrogenation reactions are first dealkylation or splitting of parafns, naphthenes or aromatics and second the saturation of aromatics. Dealkylation or splitting is favored by relatively high temperatures and low pressures whereas saturation is favored by lower temperatures and high hydrogen partial pressures. It should be noted that either temperature or pressure may be varied independently to shift the predominating reaction between splitting and saturation. Space velocity is another important variable which affects both reactions and is inversely related to reaction time. Space velocity is therefore primarily determinative of the extent to which the two reactions proceed and alects the relative amount of splitting or saturation to the extent that the reaction rates of these two reactions diifer.

Indirect measurements of the splitting phenomena are reflected by the quantity of light ends produced. The degree of saturation is indicated by the relative decrease in aromatic content. Under conditions of saturation, Example A, relatively few light ends are produced and the aromatic content, as indicated by the aromatic content of the hydrorelined lubricating oil quality given in Table II, is low. Under these conditions, 548 cubic feet of hydrogen per barrel of oil are consumed. Extensive splitting saturation is secured in Example B as indicated by the yield structure and aromatic content of the lubricating oil fraction. It will be noted that hydrogen consumption is very high for this type of operation, 1020 cubic feet per barrel. Test C is made under conditions that lead to moderate splitting but the hydrogenation of aromatics is suppressed. As a result, a lubricating oil stock of good viscosity index is obtained in good yield and the hydrogen consumption per barrel of oil is the lowest of the three operations, that is, 342 cubic feet per barrel. The reduction in the extent of hydrogenation of aromatics in Example C may be attributed to the increase in reactor ternperature to a point wherein the equilibrium is shifted away from the saturation tendency and to a reduction inthe hydrogen partial pressure in the reactor.

The hydroreiined lubricating oil stocks from Examples A, B and C are dewaxedto produce lubricating oils of included.

TABLE n I-ydrorefz'ned lubricating oil quality Example A B C Type of run Dewaxed hydro- Split- Mild refining Satutingspliteed ration satuting stock ration Gravity, API 23. 8 28.0 30. 4 27.8 Viscosity, SUS, at 210 F. 61. 4 53. 0 46. 6 49.1 Viscosity index 70 86. 5 98. 5 94.0 Solid point, F +7 +5 +5v +5 Aromatics, percent by Wcight 30. 9.6 8.2 21.0 Carbon residue, percent 0. 11 0.01 0.008 0.02 Sulfur, percent 0.26 0.06 0.02 006 :Engiizie test, modiied CRC L-4- Piston skirt rating 4. 0 6.0 4. 8 Over-all rating 63.0 67. 0 74.8 Piston skirt deposit, g. 1. 31 0.97 0.37 Oil ring deposit, g 1. 16 0. 83 0. 30 Pan and covers- Acetone soluble, g 12. 60 12.07 2. 82 Acetonc insoluble, g 7. 42 4. 26 1. 25 Used oil- Viscosity, SUS, at 210 F 66.0 56.6 53. 7 Neutralization number 5. 7 4. 2 0. 88 Propane number 1 219 188 31 Undissolved sludge, mg./

1The product quality tests listed in Table II are standardized petroleum oil tests with the exception of the engine test, The engine test Procedure propane number, and undissolved sludge,

used is a modication of the CRC L-4-1252 Test. for the CRC L-4-1252 Test is published by the Coordinating Research Council, Inc., New York 20, N.Y. The modification used differs from the CRC Ira-1252 Test in the following particulars Babbitt bearings are used throughout the engine, unleaded fuel is used, engine speed is 2500 r..p.m., load is 0 HELP., inlet jacket temperature is not specified, oultlet jacket temperature is 212i5 F., intake air temperature is not specified, exhaust back pressure is not spec'iled, crankcase is ventilated with 1 c.f.m. of air, spark advance is 38 BTC,

duration of test is 40 engine is run one hour for warm up.

hours, no break in` is 'used but the This test procedure is employed to determ'ine the oxidation characteristics of ,the weight heavy duty crankease oils.

in milligrams of material insoluble in liquid pro The propane number is pane found e yprocedure in grams of a clarified used oil sample. Th for this test is described in the paper, Dissolved Sludge in Used Oils, Hall, F

Determination of Levin, McMillan, W. A., Ind. Eng. Chem., Anal. Ed. 11, 183 (1939) Undissolved sludge is the number of milligrams of insoluble grams of a sample of used matter found suspended in 10 lubricating oil. The 'procedure to` the paper, Motor Oil, Ed. 11, 181 (1939).

Levin, H., Towne, C. C

r this test is described in Determlnation of Undissolved Sludge in Used Ind. Eng. Chem., Anal.

Reference to Table II indicates that the hydroreiined oil from Example C, manufactured under splitting conditions, is vastly superior to that obtained under saturation or splitting-saturation conditions.

This is particularly sludge.

The high quality of the oil produced by mild splitting hydrogenation is further apparent by comparing the engine test results obtained with this oil with the tests obtained on a heavy duty motor oil manufactured by conventional reiining methods from a similar crude oil.

Examples of conventially refined oils of slightly different viscosity ranges from the same type wax distillate employed in the hydroreiining examples are given in Table III.

TABLE III .Quality of motor oil manufactured by conventional re- ]nz'ng methods from wax distillate Examples D E Engine test, modified CRC L41252 l:

Piston skirt rating 4. 7 5, 5 Over-all rating 65. 7 75. 8 Piston skirt deposit, g 0.99 0. 63 l0 Oil ring deposit, g 2 1, 26 0.84

Pan and eovers- Acetone soluble, g 10. 00 5. 14 Abetone insoluble, g 4, O5 4, 75 Fresh oil-Viscosity, SUS, at 210 F 44. 8 54.2 Used oil- Viscosity, SUS, at 210 F 5&4 72 l N eutralization number 7. 2 6. 5 Propane number 1 219 316 Undissolved sludge,1 mg. /10 g 226 143 l See footnote, Table II. 2 No. 6 oil ring 50% stuck.

2O The oils used in Examples D and E are refined from a wax distillate by solvent refining, acid treating, clay contacting and dewaxing. Typical refining yields for these process-ing steps are: solvent refining, 62.8; acid treating, 98.8; clay contacting, 98.5 and dewaxing, 80.5

volume percent. The cumulative yield of finished lubricating oil by this series of conventional refining steps is 49.5 volume percent. The hydrorelined lubricating oil yield of 79.9 volume percent shown in Table I compared with this yield of 49.5 volume percent by conventional 3 refining demonstrates the superior yield advantage which may be obtained by the process of this invention.

In comparing the data of Table II with that in Table III, it will be noted that the conventionally refined oils are substantially equivalent to the oils hydroreiined under saturation or splitting-saturation conditions. However, the oil produced by splitting hydrogenation of Example C is superior tothe conventionally refined oil on the basis of the outstanding stability shown by the used oil tests.

The engine test employed in the above examples dernonstrates the stability and resistance to oxidation of the oils tested in crankcase applications. The characteristics of stability and resistance to oxidation which are demonstrated, however, are important characteristics of oils for purposes other than crankcase lubrication. For example, it would be expected that oils showing good stability and resistance to oxidation in crankcase applications would also possess these characteristics if used as turbine oils, hydraulic oils, circulating oils, or in other applications requiring stability and. resistance to oxidation.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. In a process for the treatment of a lubricating oil stock by subjecting said stock to hydrogenation in the presence of a hydrogenation catalyst at an elevated temperature and superatmospheric pressure in admixture with added hydrogen, the improvement which comprises hydrogenating said stock at a temperature within the range of from 700 F. to 750 F, at a pressure within the range of from 1000 to 2000 p.s.i.g. and at a space velocity of from 0.5 to 2.0 volumes of lubricating oil stock per volume of catalyst per hour whereby saturation type hydrogenatiorr reactions are suppressed and not more than about one-third of the aromatic hydrocarbons present in the lubricating oil stock are converted to satu- 70 rated hydrocarbons and splitting type hydrogenation reactions are favored whereby at least a portion of the lubricating oil stock is converted to hydrocarbons having `a lower normal boiling point temperature than the normal boiling point temperature of said stock, and wherein not more than 500 cubic feet of hydrogen are consumed per barrel of oil stock during hydrogenation and thereafter separating the resulting hydrogenated oil.

2. In a process as claimed in claim 1, wherein said lubricating oil stock comprises a wax distillate fraction, the catalyst is a mixed nickel sulfide-tungsten sulde hyl drogenation catalyst and the hydrogenation conditions are: a temperature of about 732 F., a pressure of about 1500 p.s.i.g., a space velocity of about 1,0, and wherein the quantity of hydrogen consumed is about 342 cubic feet per barrel of oil.

3. Method of processing a lubricating oil stock to enhance the quality thereof, which consists essentially in hydrogenating a wax distillate fraction from a parafn base crude oil in admixture with added hydrogen and in the presence of a hydrogenation catalyst lat a temperature within the range of'from 700 to 750 F., a pressure within the range of from 1000 to 2000 p.s.i.g. and a space velocity of from y0.5 to 2.0 volumes of oil per Volume of catalyst per hour whereby saturation type hydrogenation reactions are suppressed so that no more than about one-third of the aromatic hydrocarbons pres.

ent in the lubricating oil are converted to saturated hydrocarbons and splitting type hydrogenation reactions are favored whereby at least a portion of the lubricat ing oil stock is converted to hydrocarbons having a lower normal boiling point temperature than the normal boiling point temperature of said stockand wherein not more than 500 cubic feet of hydrogen are consumed per barrel of said oil stock, recovering the resulting hydrogenated oil References Cited in the file of this patent UNITED STATES PATENTS 2,339,717 vOberiell Jan, 18, 1944 2,554,282 Voorhies May 22, 1951 2,654,696 La Porte -a Oct, 6, 1953 2,717,864 Charlet et al Sept. 13, 1955 2,734,849 Gross et al. Feb. 14, 1956 2,736,689 Stuart Q Feb. 28, 1956 

1. IN A PROCESS FOR THE TREATMENT OF A LUBRICATING OIL STOCK BY SUBJECTING SAID STOCK TO HYDROGENATION IN THE PRESENCE OF A HYDROGENATION CATALYST AT AN ELEVATED TEMPERATURE AND SUPERATMOSPHERIC PRESSURE IN ADMIXTURE WITH ADDED HYDROGEN, THE IMPROVEMENT WHICH COMPRISES HYDROGENATING SAID STOCK AT A TEMPERATURE WITHIN THE RANGE OF FROM 700* F. TO 750* F. AT A PRESSURE WITHIN THE RANGE OF FROM 1000 TO 2000 P.S.I.G. AND AT A SPACE VELOCITY OF FROM 0.5 TO 2.0 VOLUMES OF LUBRICATING OIL STOCK PER VOLUME OF CATALYST PER HOUR WHEREBY SATURATION TRYPE HYDROGENTION RACTIONS ARE SUPPRESED AND NOT 